In the late 1980s, Diana Gabaldon was a research scientist working in the field of behavioral ecology when she set out to explore a new hobby that would transform her career rather drastically.

What became the New York Times bestselling series “Outlander” began as a piece of historical fiction and a challenge Gabaldon gave herself. She wanted to write a novel, just for practice. While watching the science-fiction television series “Doctor Who,” a Scottish character from the 18th century caught her attention. He became the foundation for one of the “Outlander” main characters, Jamie Fraser.

“That was an accident,” Gabaldon said in an interview with January Magazine. “I mean, everything was an accident, amazingly. I wanted to write a book for practice to learn how to write novels. And I was thinking what would be the easiest possible kind of thing to write, and I thought maybe a mystery, because I read more of those than anything.

“And then I thought, ‘Well, mysteries have plots. I’m not sure I can do that.’ And I thought perhaps that would be a historical novel because I was a research professor. Well, I was a scientist, but I did know how to use the library and it’s easier to look things up than to make them up entirely. So I said, ‘OK. I’ll write a historical novel.”

Gabaldon had joined an online message board, an early precursor to chat rooms, on the subject of literature. In the group, a man asked for a description of what it was like to be pregnant. Having three children already, Gabaldon understood the experience, but she had also written about it. At the time, she had kept her novel writing a secret. She shared a portion of the manuscript with the online message board, which reacted to it well. She decided to share more, and to write more.

In a stroke of luck, she found a literary agent and and sold the first unfinished manuscript for “Outlander.” Although it began as a piece of historical fiction, Gabaldon’s female protagonist did not fit well into 18th-century Scotland. So the book took a turn into science fiction with the introduction of 20th-century British nurse Claire Randall, who time travels from 1945 to 1743.

Originally marketed as a romance novel, “Outlander’s” popularity later allowed the publishing company to transition the series into the fiction section. Described as part historical fiction (based around the true story of Scotland’s Charles Edward Stuart), part romance novel and part science-fiction, “Outlander” has been hard to categorize, but that has rarely defeated its popularity.

“Whenever you’re dealing with something that’s difficult to describe, that you can’t get across to someone in a sound bite, it sounds like the normal default is to pick what’s easiest, and in the case of fiction written by women, fiction involving women, fiction involving any sort of relationship, the word that comes to mind is romance,” Gabaldon said in an interview with Vulture. “It’s canned stuff: ‘It’s steamy, it’s stirring, it’s sizzling, it’s a bodice ripper.’ And as I say, in romance novels, those are courtship stories. Once the couple is married, that’s the end of the story. And in our story, that means we would have stopped at episode seven.

“I’ve never seen anyone deal in a literary way with what it takes to stay married for more than 50 years, and that seemed like a worthy goal. On one level, this series is telling the story of how people stay married for a long time.”

The original “Outlander” book was published in 1991. Since then, Gabaldon has finished seven more books in the series, with a forthcoming ninth in the works. The “Outlander” series has been published in 26 countries and 23 languages and now includes several companion series. It has sold more 28 million copies in print.

In 2013, Starz revealed a television adaption of 16 episodes. It premiered in 2014 and was renewed for a fourth season in 2016. The third season aired in September and the fourth season is now being filmed. The television adaption has been nominated for several awards, including multiple Emmys and Golden Globes.

Soon after the second book, Gabaldon retired from her science career to focus on writing. She holds degrees in zoology, marine biology and a doctorate in quantitative behavioral ecology.

Tickets for her opening address at the 2018 Savannah Book Festival sold out in minutes.

“Diana Gabaldon, like Oprah, could run for president,” said Kim Bockius-Suwyn, executive director the festival. “I have to remind people we’re a literary festival. Diana’s fans are hysterical. They crashed our website.”